Summary

Sick of GXL battery dying (2 dead oem battery) decided to hack an external power tool battery instead

0.2mm layer

Print 45 degree on bed should fit Ender 3 235mm bed.

1) Remove existing battery, unscrew top and bottom cap containing terminal pins from battery main body.
2) Unwrap battery wrapper.
3) Cut Thick black wire as close to the BMS circuit board as possible (really need to cut right by the PCB)
4) Cut thick red wire that is solder into battery right below BMS circuit board
(IMPORTANT: There are 2 thick red wire, DO NOT Cut the red wire that go all the way to the bottom cap)
5) Drill access hole on the side of the post below the 2 screw hole for the hook
6) Assemble the battery top and battery bottom to the top and bottom terminal caps (re use screws, careful not to strip the top)
7) Reuse inter-section pins to join battery top to battery bottom (will need to drill out starter hole to fit the pins)
8) Use Wide foil tape or some sort for added strength to prevent top and bottom separation (Do a good job you don't want them separated or it will be tough to remove in the future)
9) Use WAGO or similar to splice the thick black wire and red wire to a long wire for connecting to external battery i suggest at least 12" (they should be in the hollow space in battery top) I used 18 awg wires and they seem to be enough
10) insert assembly, pay attention to the bottom contact/key orientation
11) half way through, insert the 2 wires you spliced and slide down the side with the hole you drilled and fish the wire out of the hole.
12) finish reassemble the handle assembly.
13) wire to external battery

Battery options
2x 18v -20v power tool batteries in series
1x 40v power tool battery (or 2x in Parallel for spreading the current draw and increased capacity)
36v scooter replacement battery

Optional in line fuse to prevent over draw from battery